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gabe-sherman opened this issue May 17, 2025 · 6 comments
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UnboundLocalError in email._header_value_parser.parse_message_id #134152

gabe-sherman opened this issue May 17, 2025 · 6 comments
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stdlib Python modules in the Lib dir topic-email type-bug An unexpected behavior, bug, or error

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@gabe-sherman
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gabe-sherman commented May 17, 2025 •
edited by hugovk
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During fuzzing of Python standard libraries, the following code snippet causes an UnboundLocalError with the following message: UnboundLocalError: cannot access local variable 'pos' where it is not associated with a value'. This occurs in the _get_ptext_to_endchars function at line 1035 in email/_header_value_parser.py.

import email._header_value_parser
email._header_value_parser.parse_message_id("<T@[")

Exception Trace

Traceback (most recent call last):
  File "/usr/lib/python3.12/email/_header_value_parser.py", line 2118, in get_msg_id
    token, value = get_dot_atom_text(value)
                   ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/email/_header_value_parser.py", line 1344, in get_dot_atom_text
    raise errors.HeaderParseError("expected atom at a start of "
email.errors.HeaderParseError: expected atom at a start of dot-atom-text but found '['

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "rep.py", line 2, in <module>
    email._header_value_parser.parse_message_id("<T@[")
  File "/usr/lib/python3.12/email/_header_value_parser.py", line 2149, in parse_message_id
    token, value = get_msg_id(value)
                   ^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/email/_header_value_parser.py", line 2121, in get_msg_id
    token, value = get_no_fold_literal(value)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/email/_header_value_parser.py", line 2066, in get_no_fold_literal
    token, value = get_dtext(value)
                   ^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/email/_header_value_parser.py", line 1557, in get_dtext
    ptext, value, had_qp = _get_ptext_to_endchars(value, '[]')
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/email/_header_value_parser.py", line 1033, in _get_ptext_to_endchars
    pos = pos + 1
          ^^^
UnboundLocalError: cannot access local variable 'pos' where it is not associated with a value

CPython versions tested on:

3.12, 3.11, 3.10, 3.9

Operating systems tested on:

Linux

Linked PRs
@gabe-sherman gabe-sherman added the type-bug An unexpected behavior, bug, or error label May 17, 2025
@picnixz picnixz added stdlib Python modules in the Lib dir topic-email labels May 17, 2025
@picnixz picnixz changed the title 'UnboundLocalError' in parse_message_id 'UnboundLocalError' in email._header_value_parser.parse_message_id May 17, 2025
@picnixz picnixz mentioned this issue May 18, 2025
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@ZeroIntensity
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Do we want to fix private APIs?

@picnixz
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picnixz commented May 18, 2025 •
edited
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In general no, but UnboundLocalError is pretty much a real issue, even in a private API, so I think we should fix this one at least. We don't need to fix the HeaderParseError, but we need to fix the UnboundLocalError.

@sergey-miryanov
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I have a patch, want to send it in a couple of hours.

@bedevere-app bedevere-app bot mentioned this issue May 18, 2025
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@sergey-miryanov
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@picnixz Please take a look.

@picnixz picnixz changed the title 'UnboundLocalError' in email._header_value_parser.parse_message_id UnboundLocalError in email._header_value_parser.parse_message_id May 18, 2025
@bedevere-app bedevere-app bot mentioned this issue May 19, 2025
Merged
sergey-miryanov added a commit to sergey-miryanov/cpython that referenced this issue May 19, 2025
@sergey-miryanov
Merge branch 'pythongh-134152-fix-unbound-local-error-in-email' of gi…
1ff7bcb 
…thub.com:sergey-miryanov/cpython into pythongh-134152-fix-unbound-local-error-in-email
bitdancer added a commit that referenced this issue May 25, 2025
@bitdancer
gh-134152: Fix UnboundLocalError in email._header_value_parser _get_p…
a32ea45 
…text_to_endchars (#134233)

Fix an UnboundLocalError that can occur when parsing certain delimited constructs in headers (domain literals, quoted strings, comments). After the fix the _get_ptext_to_endchars returns an empty string if there is no content after the opening delimiter. The calling code is responsible for handling the lack of the trailing delimiter, which it already does; this edge case was the header ending immediately after the opening delimiter.
miss-islington pushed a commit to miss-islington/cpython that referenced this issue May 25, 2025
@bitdancer @miss-islington
pythongh-134152: Fix UnboundLocalError in email._header_value_parser …
6f8d717 
…_get_ptext_to_endchars (pythonGH-134233)

Fix an UnboundLocalError that can occur when parsing certain delimited constructs in headers (domain literals, quoted strings, comments). After the fix the _get_ptext_to_endchars returns an empty string if there is no content after the opening delimiter. The calling code is responsible for handling the lack of the trailing delimiter, which it already does; this edge case was the header ending immediately after the opening delimiter.
(cherry picked from commit a32ea45)

Co-authored-by: R. David Murray <rdmurray@bitdance.com>
miss-islington pushed a commit to miss-islington/cpython that referenced this issue May 25, 2025
@bitdancer @miss-islington
pythongh-134152: Fix UnboundLocalError in email._header_value_parser …
cfa70b1 
…_get_ptext_to_endchars (pythonGH-134233)

Fix an UnboundLocalError that can occur when parsing certain delimited constructs in headers (domain literals, quoted strings, comments). After the fix the _get_ptext_to_endchars returns an empty string if there is no content after the opening delimiter. The calling code is responsible for handling the lack of the trailing delimiter, which it already does; this edge case was the header ending immediately after the opening delimiter.
(cherry picked from commit a32ea45)

Co-authored-by: R. David Murray <rdmurray@bitdance.com>
This was referenced May 25, 2025
Merged
Merged
hugovk pushed a commit that referenced this issue May 26, 2025
@miss-islington @bitdancer
[3.14] gh-134152: Fix UnboundLocalError in email._header_value_parser…
1ce68f6 
… _get_ptext_to_endchars (GH-134233) (#134678)

Co-authored-by: R. David Murray <rdmurray@bitdance.com>
hugovk pushed a commit that referenced this issue May 26, 2025
@miss-islington @bitdancer
[3.13] gh-134152: Fix UnboundLocalError in email._header_value_parser…
08e1ba8 
… _get_ptext_to_endchars (GH-134233) (#134677)

Co-authored-by: R. David Murray <rdmurray@bitdance.com>
hugovk added a commit to sergey-miryanov/cpython that referenced this issue May 26, 2025
@hugovk
Merge branch 'main' into pythongh-134152-fix-unbound-local-error-in-e…
ce7e373 
…mail
@picnixz picnixz closed this as completed May 26, 2025
@picnixz picnixz reopened this May 26, 2025
@picnixz
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picnixz commented May 26, 2025

Is it actually entirely fixed by #134233?

@bitdancer
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The issue reported here is. In the course of testing sergey-miryanov also noticed a related but separate bug, which was already separately reported in #134155, which is fixed by his PR that will land soonish.

sergey-miryanov added a commit to sergey-miryanov/cpython that referenced this issue May 26, 2025
@sergey-miryanov
Merge branch 'main' into pythongh-134152-fix-unbound-local-error-in-e…
848a218 
…mail
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